Gimp: Color to alpha

gimp

I have an image where I want all the pixels with a specific color converted to transparent pixels. The operation should not change the color/alpha value of any pixel which don't match the color exactly. How do I do that?

At first I thought I could use Colors->"Color to Alpha" but that don't work because it changes the color of all pixels(It adds an alpha value to all pixels).

Using Gimp 2.6.11 on Linux

Best Answer

You do use the Color to Alpha tool, but you also need to isolate the color using the Select by color tool. Here is how I accomplished replacing a specific color to transparent:

  • Create a new, transparent layer at the bottom of the layer stack.
  • Use the Select by Color tool to isolate the color. Be sure to set threshold = 0.0;
  • Now that you have the selection, use the Color to alpha tool, and use the eyedropper (after double clicking the "from" color) to select your color.
  • Click OK (twice).

Let me know if this works for you, or if you need me to clarify any further.

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